High-altitude wind velocity at Oukaimeden observatory

Abstract

This paper aims at studying the wind at 200 mbar over the Moroccan observatory Oukaimeden, as high‐altitude winds have been adopted as a useful parameter for site characterization in terms of the suitability of a site for the development of some adaptive optics techniques. The data used come from the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data base, which is widely acknowledged as being reliable. Statistical analyses of 200‐mbar wind speed since 1983 are performed. Comparison with some of the main observatory sites worldwide qualifies Oukaimeden as one of the best observatory sites in terms of 200‐mbar wind statistics. Our analysis of a record of seeing measurements during the years 2003 and 2004 concludes that while 200‐mbar wind speed can be used as a parameter for ranking astronomical sites in term of their suitability for adaptive optics, it cannot be used for the whole atmospheric seeing prediction. A comparison of monthly values of the seeing parameter at Oukaimeden, La Silla and Paranal demonstrates the high seeing quality of Oukaimeden, as the seeing values measured were lower than those of La Silla and Paranal for most of the time during the comparison period. Furthermore, a statistical analysis of atmospheric stratified seeing, wavefront coherence time and isoplanatic angle measured with a Multi‐Aperture Scintillation Sensor instrument over Paranal from 2004 to 2007 have been performed. We found good correlations between 200‐mbar wind velocity and levels 4, 5 and 6 seeing, wavefront coherence time and isoplanatic angle, with corresponding correlation coefficients of 0.74, 0.79, 0.70, 0.97 and 0.78.

Meteorological profiles and optical turbulence in the free atmosphere with NCEP/NCAR data at Oukaïmeden - I. Meteorological parameters analysis and tropospheric wind regimes

“…The same tendency has been registered at Observatorio del Roque de los Muchachos (ORM) by Muñon‐Tuñon, Vernin & Varela (1997) and García‐Lorenzo et al (2009). In addition, the high‐altitude wind speed statistics has been already used as a parameter for ranking for AO (Ilyasov, Tillayev & Ehgamberdiev 2000; Sarazin 2002; Carrasco & Sarazin 2003; Chueca et al 2003; Carrasco, Avila & Carramiñana 2005; García‐Lorenzo et al 2005; Bounhir et al 2009). On the basis of Sarazin & Tokovinin (2002) relationship, it becomes necessary to find a relation between and specific to each astronomical site because of differences in the vertical wind speed distributions.…”

Wind speed vertical distribution at Mt Graham

“…More precisely, the ECMWF analyses have been used at mid‐latitude sites (Masciadri & Garfias 2001; Egner et al 2007; Masciadri et al 2010) as well as at extreme latitudes (Geissler & Masciadri 2006; Hagelin et al 2008). The NOAA/NCEP re‐analyses (vertical profiles) have been used at mid‐latitude sites (Carrasco et al 2005; Avila et al 2006; Bounhir et al 2009) and the ECMWF re‐analyses (ERA) data have been used at extreme latitudes (Sadibekova et al 2006). Model outputs have shown good correlations with measurements in all cases in which this has been calculated.…”

Astroclimatic Conditions at the Hoa Lac and Nha Trang Astronomical Observatories

“…Comparison of median values obtained with other astronomical sites shows that the median at the Nha Trang observatory (14.8 m/s) is lower than medians estimated for the La Silla (31.2 m/s), Paranal (28.1 m/s), or Maidanak (25.9 m/s) [9]. At the Hoa Lac observatory the median (18.6 m/s) is close to the values at the Sierra Negra (18.3 m/s), Special Astrophysical Observatory (19.8 m/s), Oukaimeden (20.3 m/s), La Palma (20.8 m/s), Mauna Kea (21.0 m/s), and higher than the median at the Costa Rica (7.7 m/s) [9,23].…”

“…The practice of applying reanalysis data in studies of astroclimate in the world is widespread. For example, astroclimatic parameters by means of reanalysis are defined for the Canary Islands observatories, Oukaimeden observatory, and other sites [9,10].…”